A portable fuel cell electric power generator is disclosed, suitable for use as a UPS (100), including a fuel cell assembly (200), a power conditioning system (160) including a DC to DC converter and a DC to AC inverter, a plurality of metal hydride canisters (300), a manifold assembly (320), and a battery system (150), all enclosed in a mobile chassis (130). The fuel cell assembly includes a compressor (230) for providing compressed air to the fuel cell stack (210) and a condenser for condensing water vapor generated by the fuel cell stack. The canisters provide hydrogen to the fuel cells, and can be hot swapped such that the generator can operate continuously for an indefinite period. The battery system provides start-up power to the compressor, as well as initial back up power for the power outlet during fuel cell start-up. A heat transfer device (307) in the canisters aids in maintaining the desired temperature in the metal hydride. An air flow system including a fan (24) and cowling (245) direct air over the fuel cell stack to remove excess heat, and past the canisters to warm the canisters.